CVE-2025-21806: linux
Vulnerability summary
CVE-2025-21806 is a medium (CVSS 5.5) vulnerability in linux. EPSS estimates a 0.23% chance of exploitation in the next 30 days, higher than 12.6% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 55 · Related 53Timeline
- 27-02-2025PublishedVulnerability first disclosed.
- 15-10-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: net: let net.core.dev_weight always be non-zero The following problem was encountered during stability test: (NULL net_device): NAPI poll function process_backlog+0x0/0x530 \ returned 1, exceeding its budget of 0. ------------[ cut here ]------------ list_add double add: new=ffff88905f746f48, prev=ffff88905f746f48, \ next=ffff88905f746e40. WARNING: CPU: 18 PID: 5462 at lib/list_debug.c:35 \ __list_add_valid_or_report+0xf3/0x130 CPU: 18 UID: 0 PID: 5462 Comm: ping Kdump: loaded Not tainted 6.13.0-rc7+ RIP: 0010:__list_add_valid_or_report+0xf3/0x130 Call Trace: ? __warn+0xcd/0x250 ? __list_add_valid_or_report+0xf3/0x130 enqueue_to_backlog+0x923/0x1070 netif_rx_internal+0x92/0x2b0 __netif_rx+0x15/0x170 loopback_xmit+0x2ef/0x450 dev_hard_start_xmit+0x103/0x490 __dev_queue_xmit+0xeac/0x1950 ip_finish_output2+0x6cc/0x1620 ip_output+0x161/0x270 ip_push_pending_frames+0x155/0x1a0 raw_sendmsg+0xe13/0x1550 __sys_sendto+0x3bf/0x4e0 __x64_sys_sendto+0xdc/0x1b0 do_syscall_64+0x5b/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e The reproduction command is as follows: sysctl -w net.core.dev_weight=0 ping 127.0.0.1 This is because when the napi's weight is set to 0, process_backlog() may return 0 and clear the NAPI_STATE_SCHED bit of napi->state, causing this napi to be re-polled in net_rx_action() until __do_softirq() times out. Since the NAPI_STATE_SCHED bit has been cleared, napi_schedule_rps() can be retriggered in enqueue_to_backlog(), causing this issue. Making the napi's weight always non-zero solves this problem. Triggering this issue requires system-wide admin (setting is not namespaced).
CVSS metrics
3 scores · 3 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.23%
Chance of exploitation in the next 30 days
Percentile
13%
Versus all other CVEs
30-day change
+0.01 pp
From 0.21% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeNo weakness data has been published for this record.
Affected systems
Ubuntu137 products
- linuxAll versions (No fix recorded) | < 5.4.0-216.236 | < 5.15.0-140.150 | < 6.8.0-64.67
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 5.4.0-1146.156 | < 5.15.0-1084.91 | < 6.8.0-1032.34
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ e3876605450979fe52a1a03e7eb78a89bf59e76a, < d0e0f9c8218826926d7692980c98236d9f21fd3c | ≥ e3876605450979fe52a1a03e7eb78a89bf59e76a, < c337c08819a4ec49edfdcd8fc46fbee120d8a5b2 | ≥ e3876605450979fe52a1a03e7eb78a89bf59e76a, < 0e2f1d93d287d544d26f8ff293ea820a8079b9f8 | ≥ e3876605450979fe52a1a03e7eb78a89bf59e76a, < 5860abbf15eeb61838b5e32e721ba67b0aa84450 | ≥ e3876605450979fe52a1a03e7eb78a89bf59e76a, < 6ce38b5a6a49e65bad163162a54cb3f104c40b48 | ≥ e3876605450979fe52a1a03e7eb78a89bf59e76a, < 33e2168788f8fb5cb8bd4f36cb1ef37d1d34dada | ≥ e3876605450979fe52a1a03e7eb78a89bf59e76a, < 1489824e5226a26841c70639ebd2d1aed390764b | ≥ e3876605450979fe52a1a03e7eb78a89bf59e76a, < d1f9f79fa2af8e3b45cffdeef66e05833480148a | 2.6.12
- linux_kernel≥ 2.6.13, < 5.4.291 | ≥ 5.5, < 5.10.235 | ≥ 5.11, < 5.15.179 | ≥ 5.16, < 6.1.129 | ≥ 6.2, < 6.6.76 | ≥ 6.7, < 6.12.13 | ≥ 6.13, < 6.13.2 | 2.6.12
Debian1 product
- linux< 6.1.129-1 | < 6.12.13-1
3 vendors · 140 products
